/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.server;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.Principal;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.InvalidMediaTypeException;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.LinkedCaseInsensitiveMap;
import org.springframework.util.StringUtils;

/**
 * {@link ServerHttpRequest} implementation that is based on a {@link HttpServletRequest}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.0
 */
public class ServletServerHttpRequest implements ServerHttpRequest {

    protected static final String FORM_CONTENT_TYPE = "application/x-www-form-urlencoded";

    protected static final Charset FORM_CHARSET = StandardCharsets.UTF_8;


    private final HttpServletRequest servletRequest;

    @Nullable
    private URI uri;

    @Nullable
    private HttpHeaders headers;

    @Nullable
    private ServerHttpAsyncRequestControl asyncRequestControl;


    /**
     * Construct a new instance of the ServletServerHttpRequest based on the
     * given {@link HttpServletRequest}.
     *
     * @param servletRequest the servlet request
     */
    public ServletServerHttpRequest(HttpServletRequest servletRequest) {
        Assert.notNull(servletRequest, "HttpServletRequest must not be null");
        this.servletRequest = servletRequest;
    }


    /**
     * Returns the {@code HttpServletRequest} this object is based on.
     */
    public HttpServletRequest getServletRequest() {
        return this.servletRequest;
    }

    @Override
    @Nullable
    public HttpMethod getMethod() {
        return HttpMethod.resolve(this.servletRequest.getMethod());
    }

    @Override
    public String getMethodValue() {
        return this.servletRequest.getMethod();
    }

    @Override
    public URI getURI() {
        if (this.uri == null) {
            String urlString = null;
            boolean hasQuery = false;
            try {
                StringBuffer url = this.servletRequest.getRequestURL();
                String query = this.servletRequest.getQueryString();
                hasQuery = StringUtils.hasText(query);
                if (hasQuery) {
                    url.append('?').append(query);
                }
                urlString = url.toString();
                this.uri = new URI(urlString);
            } catch (URISyntaxException ex) {
                if (!hasQuery) {
                    throw new IllegalStateException(
                            "Could not resolve HttpServletRequest as URI: " + urlString, ex);
                }
                // Maybe a malformed query string... try plain request URL
                try {
                    urlString = this.servletRequest.getRequestURL().toString();
                    this.uri = new URI(urlString);
                } catch (URISyntaxException ex2) {
                    throw new IllegalStateException(
                            "Could not resolve HttpServletRequest as URI: " + urlString, ex2);
                }
            }
        }
        return this.uri;
    }

    @Override
    public HttpHeaders getHeaders() {
        if (this.headers == null) {
            this.headers = new HttpHeaders();

            for (Enumeration<?> names = this.servletRequest.getHeaderNames(); names.hasMoreElements(); ) {
                String headerName = (String) names.nextElement();
                for (Enumeration<?> headerValues = this.servletRequest.getHeaders(headerName);
                     headerValues.hasMoreElements(); ) {
                    String headerValue = (String) headerValues.nextElement();
                    this.headers.add(headerName, headerValue);
                }
            }

            // HttpServletRequest exposes some headers as properties:
            // we should include those if not already present
            try {
                MediaType contentType = this.headers.getContentType();
                if (contentType == null) {
                    String requestContentType = this.servletRequest.getContentType();
                    if (StringUtils.hasLength(requestContentType)) {
                        contentType = MediaType.parseMediaType(requestContentType);
                        this.headers.setContentType(contentType);
                    }
                }
                if (contentType != null && contentType.getCharset() == null) {
                    String requestEncoding = this.servletRequest.getCharacterEncoding();
                    if (StringUtils.hasLength(requestEncoding)) {
                        Charset charSet = Charset.forName(requestEncoding);
                        Map<String, String> params = new LinkedCaseInsensitiveMap<>();
                        params.putAll(contentType.getParameters());
                        params.put("charset", charSet.toString());
                        MediaType mediaType = new MediaType(contentType.getType(), contentType.getSubtype(), params);
                        this.headers.setContentType(mediaType);
                    }
                }
            } catch (InvalidMediaTypeException ex) {
                // Ignore: simply not exposing an invalid content type in HttpHeaders...
            }

            if (this.headers.getContentLength() < 0) {
                int requestContentLength = this.servletRequest.getContentLength();
                if (requestContentLength != -1) {
                    this.headers.setContentLength(requestContentLength);
                }
            }
        }

        return this.headers;
    }

    @Override
    public Principal getPrincipal() {
        return this.servletRequest.getUserPrincipal();
    }

    @Override
    public InetSocketAddress getLocalAddress() {
        return new InetSocketAddress(this.servletRequest.getLocalName(), this.servletRequest.getLocalPort());
    }

    @Override
    public InetSocketAddress getRemoteAddress() {
        return new InetSocketAddress(this.servletRequest.getRemoteHost(), this.servletRequest.getRemotePort());
    }

    @Override
    public InputStream getBody() throws IOException {
        if (isFormPost(this.servletRequest)) {
            return getBodyFromServletRequestParameters(this.servletRequest);
        } else {
            return this.servletRequest.getInputStream();
        }
    }

    @Override
    public ServerHttpAsyncRequestControl getAsyncRequestControl(ServerHttpResponse response) {
        if (this.asyncRequestControl == null) {
            if (!ServletServerHttpResponse.class.isInstance(response)) {
                throw new IllegalArgumentException(
                        "Response must be a ServletServerHttpResponse: " + response.getClass());
            }
            ServletServerHttpResponse servletServerResponse = (ServletServerHttpResponse) response;
            this.asyncRequestControl = new ServletServerHttpAsyncRequestControl(this, servletServerResponse);
        }
        return this.asyncRequestControl;
    }


    private static boolean isFormPost(HttpServletRequest request) {
        String contentType = request.getContentType();
        return (contentType != null && contentType.contains(FORM_CONTENT_TYPE) &&
                HttpMethod.POST.matches(request.getMethod()));
    }

    /**
     * Use {@link javax.servlet.ServletRequest#getParameterMap()} to reconstruct the
     * body of a form 'POST' providing a predictable outcome as opposed to reading
     * from the body, which can fail if any other code has used the ServletRequest
     * to access a parameter, thus causing the input stream to be "consumed".
     */
    private static InputStream getBodyFromServletRequestParameters(HttpServletRequest request) throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream(1024);
        Writer writer = new OutputStreamWriter(bos, FORM_CHARSET);

        Map<String, String[]> form = request.getParameterMap();
        for (Iterator<String> nameIterator = form.keySet().iterator(); nameIterator.hasNext(); ) {
            String name = nameIterator.next();
            List<String> values = Arrays.asList(form.get(name));
            for (Iterator<String> valueIterator = values.iterator(); valueIterator.hasNext(); ) {
                String value = valueIterator.next();
                writer.write(URLEncoder.encode(name, FORM_CHARSET.name()));
                if (value != null) {
                    writer.write('=');
                    writer.write(URLEncoder.encode(value, FORM_CHARSET.name()));
                    if (valueIterator.hasNext()) {
                        writer.write('&');
                    }
                }
            }
            if (nameIterator.hasNext()) {
                writer.append('&');
            }
        }
        writer.flush();

        return new ByteArrayInputStream(bos.toByteArray());
    }

}
